Many useful fluids have been prepared by dispersing comminuted solids therein. Such fluids may have relatively great utility, if certain qualities or characteristics are present. These qualities or characteristics may be highly reliant upon the amount of the comminuted solid is present in the fluid, or how much of one or more critical components of the comminuted solid has been extracted therefrom and dispersed within the fluid.
In one example of the present disclosure, brewing coffee has been part of our culture for centuries. Today, there are three main methods of brewing coffee: gravitational percolation such as drip brewing, infusion through steeping such as a French press and pressurized percolation such as espresso. The common thread of all coffee brewing is the proper extraction of the coffee that produces the desired strength for personal taste or regional preferences. The “ideal” cup of coffee has the optimum balance of extraction and strength for a brew method and type of coffee.
It is generally agreed among the various coffee associations that the ideal coffee extraction should range from 18 percent to 22 percent. However, the recommended range for strength is 1.15 percent to 1.35 percent for the Specialty Coffee Association of America (SCAA), 1.20 percent to 1.45 percent for the Specialty Coffee Association of Europe (SCAE), and 1.30 percent to 1.55 percent for the Norwegian Coffee Association (NCA). These organizations confirm that coffee strength preferences are regional as well as personal.
Each of these organizations sponsor the “Golden Cup Award” to those coffee purveyors who have proven their ability to brew coffee to defined standards of quality. The SCAA defines five points of quality: (1) proper ratio of coffee to water, (2) proper grind, (3) proper equipment operation, (4) good water, and (5) clean equipment. In order to qualify for the Golden Cup Award, the coffee formula must fall between 92 grams and 120 grams of coffee for 1.9 liter of water, resulting in strength from 1.15 percent to 1.35 percent as the amount of total dissolved solids which is commonly represented as TDS percent. Each of these organizations publish a “Coffee Brewing Control Chart” that graphically parameterize extraction (solubles yield), strength percent (solubles concentration), and brew ratio (mass coffee to volume water). The chart assumes the brewing method is drip percolation with a constant absorption factor built into the formulas. The absorption factor relates to the amount of fluid that is retained in the coffee bed of grounds.
The Coffee Brewing Control Chart is referenced in U.S. Pat. No. 7,952,697, which is incorporated herein by reference. The Coffee Brewing Control Chart has served the industry well for several years but lacks the flexibility to adapt to alternative brewing methods. The Coffee Brewing Control Chart was developed using drip brewers and does not consider immersion or espresso type brewers. There are many types of brewer apparatus in existence and many of them would require a custom chart for proper coffee brewing to meet these standards.
There are additional essential elements to brewing good coffee. The coffee grind quality and size distribution will affect extraction and taste over brew time. Adjusting the grind size is the most effective way to control bitterness and astringency but is never mentioned in U.S. Pat. No. 7,952,697, nor used within the Coffee Brewing Control Chart. The brewing method or equipment must control contact time, water temperature and turbulence. The SCAA and industry leaders teach that “particle size dictates brew time” (Ephraim, D., 2010 Optimizing Brewed Coffee Quality through Proper Grinding. SCAA Event Lecture). For example, the fine grind of an espresso under pressure will require a much shorter contact time than a traditional automatic drip brewer that uses a coarse grind without pressure. However, brew time is not easily adjusted for the majority of brewing apparatus which have a fixed dispersion rate of hot water onto the coffee bed of grounds. The brewer temperature as the water is emerging onto the coffee bed should be between 92 to 96 degrees C., per the SCAA. Lower temperatures will not extract properly and will result in a weak brew. Higher temperatures result in an over-extraction and contribute to the astringency and/or bitterness of the coffee. Turbulence is the amount of mixing action or agitation used during the brewing cycle. Turbulence will also cause a temporary increase in coffee extraction and assist in creating a uniform dispersion of water around the coffee grounds. Each brewing method and equipment will have its own ideal brewing settings or recipes. This is the art of brewing and will determine the best values for each brewing parameter for each individual or regional preference and type of coffee.
Because coffee consists of over 98 percent water, the quality of the water will affect extraction rate and overall taste. Water quality must be controlled for accurate coffee brewing. There are ideal ranges of TDS (125 to 175 mg/l), hardness (1-7 gr), calcium (17-120 mg/l) and an absence of iron and chlorine. Dissolved solids actually contribute to good taste; so pure water is never used.
Another element that contributes to coffee brewing quality is the filtering medium. The choices will depend on the brewing equipment and method. Cloth filters were the first used and are still in use today. The most common are the micro-etched metal screens and paper filters. The amount of residue or sediment allowed to pass through the filter will affect the mouth feel of the coffee but may also become an irritant for some people.
Brewing a superior cup of coffee requires control of more parameters than the three major ones described in the traditional Coffee Brewing Control Chart, such as that depicted in FIG. 1. A more comprehensive approach to determining the ideal brew ratio is needed that uses the mean coffee grind size as an input parameter as well as all the essential contributors to the coffee brewing method.
Coffee grind size distribution is critical in evaluating and determining coffee extraction characteristics. Coffee grinders are not calibrated to established standards and are adjusted to proprietary markings from fine to course. Without a known mean grind size, predictions of coffee extraction are inaccurate. Additionally, reproducing a coffee recipe accurately using different grinders is possible if the grinders are calibrated to each other. When the user can provide a measured average grind size, the coffee model's accuracy is greatly improved and as a result, its predictions of coffee extraction. Conventionally, coffee grind size or the particle profile is not often calculated due to expensive or labor intensive equipment. The three primary methods of determining particle size distributions are calibrated sieving trays, laser diffraction, and image analysis.
Coffee grind analysis may be performed using stacked screen sieves corresponding to U.S. standard sieves numbers 12, 16, 20 and 30. The sample is placed in the top sieve corresponding to the coarsest screen and covered. Normally, the sieve stack is placed on a mechanical shaker for 5 minutes and then each sieve weighed to determine the particle size profile. Laser diffraction is based on the principal that the intensity of the light scattered by a particle is directly proportional to the particle size. The laboratory equipment used for laser diffraction is bulky and very expensive besides having inaccuracies when measuring non-spherical particles such as coffee grounds. Computer image analysis offers very accurate representation of irregular shaped objects that are clearly delineated from the image's background or other particles. Dispersing the particles without overlap is the primary challenge using this technique.
Reducing coffee “fines” to an acceptable level is critical for eliminating over extracted coffee which results in bitter taste. This, along with a graphical representation of grind distribution, is extremely important in conveying a coffee taste profile from cupping the same coffee within distribution channels.
There remains a need in the prior art for improved ways of modeling the characteristics of brewed coffee.